The general purpose of the proposed research is to identify and characterize the agents derived from immunologically active lymphocytes and similar factors from other cell types which are able to modulate the motility of tumor cells in vitro. Certain tumor cells can migrate from capillary tubes and such migration can be used to examine various tumor cell-host interactions. We have already reported that migration of mastocytoma cells was readily inhibited by lymphocyte culture supernatants (lymphokines) containing macrophage migration inhibitory factor (MIF). We will continue studies designed to explore the range of various tumor cells whose migration from capillary tubes can be inhibited by such supernatants, and in addition, will attempt to characterize the effector substances by physicochemical analysis as well as to determine antigenic properties of substance(s). Furthermore, the ability of producing such factors in vivo by host animals will be examined in detail. Effects of exogeneously administered lymphokines on in vivo tumors will also be explored especially as to the metastasis of tumor cells. Since anti-tumor antisera and concanavalin A besides lymphokines are also known to inhibit the in vitro migration of murine lymphoma cells, basic mechanisms of tumor cell migration inhibition will be analyzed by comparing the effects on tumor cells of those various agents. These studies will be performed in order to characterize a form of immunologic response of the host to tumor cells which could have application in controlling the spread of tumors in vivo, and which might therefore have clinical application.